Production of acetylene



March 22, 1966 DANZ ET AL 3,242,225

PRODUCTION OF AGETYLENE Filed May 20, 1964 2 Sheets-Sheet 1 FIG. I

KPREHEATER I PREHEATER ,/M|X|NG CH 2 )E 3 CHAMBER CRACKING on. comausnonSTORAGE 4 5 CHAMBER HEAT sxcmmssn 6 QUENCH 7 02 H2 CHAMBER lNVENTORSWILLI DANZ OTTO FREY ERICH KITTEL. FERDINAND MARKERT WALTER TELTSCHIKATT'YS March 22, 1966 w. DANZ ETAL 3,42,22

PRQDUCTION OF ACETYLENE Filed May 20, 1964 2 Sheets-Sheet 2 FIG.2

INVENTORS WILLI DANZ OTTQ FREY ERICH KITTEL FERDINAND MARKERT WALTERTELTSCHIK BY f JILKVQ/IH 4 "l United States Patent 5 Claims. or. 260679)This application is a continuation-in-part of our copending applicationSerial No. 187,267, filed April 13, 1962.

This invention relates to a process for the production of acetylene fromhydrocarbons. More specifically, it relates to a process for theproduction of acetylene in which the hot acetylene-containing gases arecooled with hydrocarbon oil. 9

It is known to prepare acetylene by subjecting hydrocarbons to hightemperatures, for example by means of an electric discharge, hot flamegases or the heat liberated by incomplete combustion of hydrocarbonswith oxygen. After having been exposed to the high temperatures, thehydrocarbons must be cooled very rapidly, and thisis effected inconventional manner by quenching the hot gases with a liquid.

In the prior art methods, hydrocarbons having from one to ten carbonatoms and oxygen or oxygen-containing gas are used as initial materials,the ratio of hydrocarbon to oxygen being about 1:1 by weight. The gasesare preheated to about 150 to 700 C. prior to the reaction. In thereaction space, a maximum temperature of about 1,300 to 1,650 C. is setup by the reaction of these gases. The reaction period is about two tofive thousandths of a second. It is known to use liquids with a highboiling point, as for example mercury, for the cooling operation. It isalso known to use water for quenching the gases. The use of mercury isdangerous because mercury, especially mercury vapor, is very injuriousto health. The use of water has the disadvantage that theacetylene-containing gases are mixed with steam and the heat energycontained in the steam is usually lost because the steam cannot beutilized for performing work. In the conventional quenching of theacetylene-containing gases with water under pressure, high-pressuresteam or a condensate having a temperature above 100 C. is formed, butworking under pressure is very troublesome because complicated equipmentis required for the purpose. It is also known that hydrocarbon oilscannot be used for quenching the hot gases because the hydrocarbon oilswould be decomposed at the high temperatures involved. Moreover, it isknown to quench the hot gases in two stages with mineral oils. Duringquenching in the first stage, the mineral oils are partly cracked. Thegases, which have been slightly cooled in the first stage, are thenfurther quenched with mineral oils in a second stage. This method hasthe disadvantage that the acetylene-containing gases are contaminated bythe gases resulting from the cracking of the mineral oils.

We have found that the hot gases obtained in the production of acetylenecan be quenched in a simple way by carrying out the quenching in asingle stage with highboiling hydrocarbon oils, advantageously withhigh-boiling aromatic hydrocarbon oils, the volumetric ratio ofhydrocarbon oil to gas being at least 1:100, and separating thecarbon-black containing hot hydrocarbon oil from the gas.

The volume of the hydrocarbon oil may be measured, for example, in cubicmeters and the volume of the gas in cubic meters (S.T.P.).

3,242,225 Patented Mar. 22, 1965 In accordance with this invention, itis possible to quench the hot gas (whose temperature is about 1,500 C.or more) to about 200 C. withina short time. There is no appreciablecracking of the high-boiling aromatic hydrocarbon oils in this process,i.e., the composition of the gas is not changed by the quenching becauseno gaseous impurities, such as ethylene, are formed during theoperation. By reason of the high temperatures involved, part of thehigh-boiling aromatic hydrocarbon oils is vaporized in chemicallyunchanged form and the gas contains small droplets of the hydrocarbonoils used for quenching, but these impurities can be separated from thegas in a simple way and are not comparable with the gases resulting fromthe cracking of hydrocarbons.

By high-boiling hydrocarbon oils We mean hydrocarbon oils, especiallyaromatic hydrocarbon oils, which have boiling points of about 150 to 400C., for example polynuclear aromatic hydrocarbons. The oils should befree of paraffinic constituents, i.e., purely aromatic. An oil shouldtherefore have a pour point of 23 C. A higher pour point, e.g., a pourpoint of about 0 C. would indicate that the oil contains paralfinicconstituents in addition to the aromatics.

The volumetric ratio of hydrocarbon oil to gas should be at least 1:100,i.e., l or more parts by volume of highboiling hydrocarbon oil isrequired for quenching 100 parts by volume of hot gas. By the volume ofthe gas we mean its volume at standard conditions (S.T.P.), i.e., theamount of gas is measured, for example, in cubic meters (S.T.P.). Afterquenching, the hydrocarbon oil contains the bulk of the carbon blackoriginally present in the hot gas.

It is advantageous to remove the hydrocarbon oil vapor, entraineddroplets of hydrocarbon oil and the residual carbon black from thequenched acetylene-containing gas by means of low-boiling hydrocarbonoil, preferably low-boiling aromatic hydrocarbon oil (specific gravityless than 0.95), by washing the gas and cooling it to the boiling pointof the low-boiling hydrocarbon oil. This process offers the advantagethat the carbon black is completely removed from the gas without the useof mechanical means, such as filters. Another important advantage of theprocess is to be seen in the complete separation of the high-boilinghydrocarbon oil from the acetylenecontaining gas because, uponcondensation of the water vapor contained in the gas, any residues ofthis oil in the acetylene-containing gas willform a stable emulsion inthe condensate, and such an emulsion renders the removal of oil andwater very difiicult. By removing the carbon black without the use ofmechanical means, substantially ash-free carbon black is obtained which,after separation from the hydrocarbon oil, is a valuable by product. Inthe conventional separation of carbon black from acetylene-containinggases by means of water and coke filters, the carbon black iscontaminated by fines originating from the coke of the coke filter.Hence, the carbon black has a considerable ash content and cannot beused for conventional applications.

By low-boiling point oils we mean hydrocarbons, especially aromatichydrocarbons, which have boiling points of about to 200 C. and specificgravities of less than 0.95, especially specific gravities of from 0.87to 0.94, for example 0.90.

The difference in the boiling points of any two oils used should be from30 to 200 C., i.e., the boiling point of the high-boiling oil should befrom 30 to 200 C. higher than that of the low-boiling oil. On no accountmust the difference be less than 30 C. The low-boiling oil may consistto the extent of percent of parafiins. Provision should be made,however, that the two oils cannot intermix in application, as otherwisecracking products are liable to be formed and these would pass into andcontaminate the acetylene-containing gas if the high-boiling oil isreused for quenching purposes.

Washing of the gas with the low-boiling hydrocarbon oil may be effected,for example, by introducing the acetylene-containing gas, at atemperature of about 180 C., into the bottom of a distilling andfractionating column, allowing it to ascend therein, and adding theliquid low-boiling hydrocarbon oil at about the middle of the column.The low-boiling hydrocarbon oil vaporizes upon coming into contact withthe hot gas and abstracts the heat of vaporization from the gas. Thehigh-boiling hydrocarbon oil is thereby condensed out and can bewithdrawn at the bottom. The vapor of the low-boiling hydrocarbon oilrises in the column and is partly condensed at the top of the column. Inthis way, a reflux of lowboiling hydrocarbon oil is formed in the upperpart of the column, while a reflux of high-boiling hydrocarbon oil isformed in the lower part thereof. By these refluxes, complete separationof the high-boiling hydrocarbon oil and almost complete removal of thecarbon black from the acetylene-containing gas is accomplished. When thegases leaving the top of the column are subsequently cooled to below thedew-point of the water vapor contained in the gases, the vapors of thelow-boiling hydrocarbon oil are condensed and a condensate is obtainedin which water and hydrocarbon are present in two layers and can readilybe separated from each other.

It is advantageous to collect the high-boiling hydrocarbon oilsseparated from the gas and to use their heat energy profitably for somepurpose. The considerable amount of heat energy abstracted from the hotgas during quenching can thus be utilized for other purpose without theneed to carry out the production of acetylene under pressure, as has tobe done if the hot gases are quenched with water and the heattransferred to the water or water vapor is to be used profitably.

In the process according to this invention, the carbon black formed inthe production of acetylene is taken up by the high-boiling hydrocarbonoil. If the heat energy contained in the hot oil is recovered asdescribed above, it is advantageous to reuse the oil, from which theheat energy has been substantially abstracted in a heat exchanger, forquenching acetylene-containing gases, i.e., the high-boiling hydrocarbonoil is recycled. During each cycle, the oil takes up the carbon blackcontained in the quenched gas and thus becomes enriched in carbon black.It is advantageous to carry out this cyclic process in such a way thatthe carbon black content of the recycled high-boiling hydrocarbon oil isadjusted to a maximum of about 35% by weight by withdrawing anappropriate amount of carbon-black containing oil from the circulationand replacing it by oil which is free from carbon black or contains onlya small amount of carbon black.

The carbon black containing oil removed from the circulation may, forexample, be burnt and the carbon black thus utilized profitably in asimple way. The carbon black containing oil may obviously also be freedfrom carbon black by mechanical methods for example by means of filtersor centrifuges, and then returned to the above-mentioned circulation.

The present invention will be further described with reference to theaccompanying drawing in which FIGURE 1 is a flow-sheet showing thecourse of the process and FIGURE 2 diagrammatically illustrates anapparatus, by way of example, in which the process can be carried out.

Referring to FIGURE 1 oxygen and hydrocarbon CH are heated up inseparate preheaters 1 and 2 and mixed thoroughly in a mixer 3. Thehomogeneous mixture is passed into a combustion chamber 5, where it isconverted in a flame reaction into an acetylene-containing cracked gas,which is quenched with oil at' 7. The cracked gas is then passed on tofurther purification and into the processing plant (not shown) while theoil is recycled to 7 via a heat exchanger 6 in which steam is produced.A small portion of the carbon black containing oil is withdrawn and usedas fuel in preheaters 1 and 2. This amount of oil is replaced by freshoil from a container 4.

Referring to FIGURE 2 gasoline and oxyen are fed into a burner 10through line 8 and 9 respectively and reacted therein to acetylene. Thehot gas is quenched with a high-boiling oil at 11 and thence passes intothe washing column 12 where it is cooled with low-boiling oil fed inthrough line 13. The hot oil collects at 14 and from there flows back to11 through cooler 15 to be reused as quenching oil. The gas passesthrough line 16 into a cooler 17 to be cooled with water fed in throughline 18. The low-boiling oil collects at 19. It is stripped of water andrecycled to the washing column 12 through line 20. The water recyclesthrough line 21 and cooler 22 into the cooler 17. The cooled moistacetylene-con taining gas is discharged through line 23.

The invention will be further illustrated by, but is not limited to, thefollowing examples.

Example 1 370 kg. per hour of gasoline and 250 cubic meters (S.T.P.) perhour of oxygen are heated separately to 360 C. in two preheaters. Thetwo are mixed and converted in a burner into acetylene-containing gas.At the outlet of the burner the hot cracked gas is quenched with anaromatic hydrocarbon oil having a boiling point of 240 to 360 C., theoil being used at a rate of 40,000 kilograms per hour. The cracked gas,now at a temperature of 180 G, contains about 10% by volume of acetyleneand less than 0.5 g. of carbon black per cubic meter (S.T.P.). At thesame time, 650 kg. per hour of steam saturated at 150 C. is obtained ina heat exchanger by heat exchange with the oil.

Example 2 520 cubic meters (S.T.P.) per hour of methane and 300 cubicmeters (S.T.P.) per hour of oxygen are heated separately to 600 C. intwo preheaters. The two are mixed and converted in a combustion chamberinto aceylene-containing gas. At the outlet of the combustion chamber,the hot cracked gas is quenched with a highboiling aromatic hydrocarbonoil having a boiling point of 240 to 360 C., the oil being used at arate of 40,000 kilograms per hour. The cracked gas, now at a tem=perature of 180 C., contains about 8% by volume of acetylene and about0.3 g. of carbon black per cubic meter (S.T.P.). At the same time, 700kg. per hour of steam saturated at 150 C. is obtained by heat exchangewith the oil.

Example 3 In the manner described in Example 1 a gas with 10% ofacetylene is produced from gasoline and oxygen at a rate of 800 cubicmeters (S.T.P.) per hour. The gas which contains high boiling oil invapor form is obtained with a temperature of 180 C. It is quenched with2 cubic meters per hour of a low-boiling oil having a boiling point ofto 190 C., the temperature of the gas falling to C. The oil used forquenching is mainly aromatic containing only a very small amount ofparaflinic constituents. The vaporous high-boiling oil is condensed andthe liquid high-boiling oil is reused for quenching. The gas is furthercooled down from 100 to 30 C. by directly spraying it with water. Theend product is a moist acetylene-containing gas having a temperature of30 C. The amount of cooling water used is 20 cubic meters per hour. Thelow-boiling oil is condensed and reused for quenching the gas at C.

What we claim is:

1. In a process for the production of acetylene by subjectinghydrocarbons to a high cracking temperature of about 1300 to 1650 C.,quenching the resultant hot gas from said cracking temperature to alower temperature and separating carbon black from said gas, the improveinent which comprises: initially quenching said hot gas in a singlestage with a high-boiling quenching liquid consisting essentially of anaromatic hydrocarbon oil which has a boiling point above about 150 C.and which is stable against cracking at said high temperatures in avolumetric ratio of said oil to said gas of at least 1:100; andseparating the carbon black containing hot oil from the gas.

2. A process as claimed in claim 1 wherein the quenched gas containingacetylene and a portion of said high-boiling aromatic hydrocarbon oilwhich has been vaporized during quenching is washed with a lowboilinghydrocarbon oil having a boiling point above about 80 C. and a specificgravity of less than 0.95 and cooled to the boiling point of saidlow-boiling hydrocarbon oil.

3. A process as claimed in claim 2 wherein a low-boiling aromatichydrocarbon oil is used for said washing.

4. A process as claimed in claim 3 wherein water vapor contained in theacetylene-containing quenched gas is condensed together with saidlow-boiling aromatic hydrocarbon oil after said washing, and theresulting two layers of water and oil separated from each other.

5. A process as claimed in claim 3 wherein said highboiling aromatichydrocarbon oil has a boiling point of about 150 to 400 C. and saidlow-boiling aromatic hydrocarbon oil has a boiling point of about 80 to200 C., the difference in the boiling point of the two oils being atleast 30 up to about 200 C.

2,982,794 3,022,148 2/1962 James 260679 X 3,060,247 10/1962 Wolfram eta1 260679 ALPHONSO D. SULLIVAN, Primary Examiner.

1. IN A PROCESS FOR THE PRODUCTION OF ACETYLENE BY SUBJECTINGHYDROCARBONS TO A HIGH CRACKING TEMPERATURE OF ABOUT 1300* TO 1650*C.,QUENCHING THE RESULTANT HOT GAS FROM SAID CRACKING TEMPERATURE TO ALOWER TEMPERATURE AND SEPARATING CARBON BLACK FROM SAID GAS, THEIMPROVEMENT WHICH COMPRISES: INITIALLY QUENCHING SAID HOT GAS IN ASINGLE STAGE WITH A HIGH-BOILING QUENCHING LIQUID CONSISTING ESSENTIALLYOF AN AROMATIC HYDROCARBON OIL WHICH HAS A BOILING POINT ABOVE ABOUT150*C. AND WHICH IS STABLE AGAINST CRACKING AT SAID HIGH TEMPERATURES INA VOLUMETRIC RATIO OF SAID OIL TO SAID GAS OF AT LEAST 1:100; ANDSEPARATING THE CARBON BLACK CONTAINING HOT OIL FROM THE GAS.